The British Library lets you view over a million copyright-free images available online.
Well, I was planning on linking to it and showing some photos but they chose to use a service that blocks you from downloading the photos without signing in. Seems like a lame way to provide what could have been open access content so it doesn't seem worthy of linking to in my opinion. Hopefully they will find a better solution soon.
See the Curious Cat creative commons attribution photo feed.